net: hns: fix wrong display of "Advertised link modes"

driver inclusion
category: bugfix
bugzilla: NA
CVE: NA

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The "Advertised link modes" always shows "1000baseT/Full", because
the driver only assigned this value.

Function ethtool_convert_link_mode_to_legacy_u32() should be called
after function phy_ethtool_ksettings_get() to get the current value
of the phy.

Signed-off-by: Yonglong Liu <liuyonglong@huawei.com>
Reviewed-by: li yongxin <liyongxin1@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>